Abstracts

RATIONALE:Intracranial electrode monitoring is frequently required for the pre-surgical evaluation of epilepsy surgery. Epidural peg electrodes are a popular choice at many centers. Peg electrodes do not allow monitoring of subtemporal or subfrontal areas. Multicontact epidural cylinder electrodes are used at our center because they allow monitoring of these areas as well as the convexity. We now report our experience with epidural cylinder electrodes in 60 consecutive patients. Indications and technique of placement are also discussed. METHODS:We reviewed data in 60 patients who underwent the placement of epidural cylinder electrodes in order to evaluate safety and efficacy of this monitoring technique. All patients underwent general anesthesia and had placement of multicontact cylinder electrodes in the epidural space via burr holes. Electrodes were placed over the convexity, subtemporally, or subfrontally. RESULTS: Indications for monitoring were temporal lobe epilepsy in 30 cases and extratemporal in 30 cases. 57 of 60 patients had electrodes placed bilaterally. The number of multicontact (4-10) electrodes placed ranged from one to eight. The monitoring period lasted from one to three weeks. In 33% of cases epidural electrodes were combined with subdural electrodes. More than two-thirds of patients were found to be candidates for surgery. No patients required additional electrode monitoring. In two cases, subdural hematomas required evacuation but caused no permanent neurological injury. There were no mortalities. CONCLUSIONS: Epidural cylinder electrodes are a useful addition to the options of intracranial electrode monitoring. They are particularly useful in cases where bitemporal epilepsy must be ruled out. In these cases, they allow monitoring of the temporal convexity and the mesial temporal region up to the area of the gasserian ganglion via the epidural space. This eliminates the need for foramen ovale elecrodes and is a technical advantage over peg electrodes. Epidural cylinder monitoring avoids the problems of CSF leak, allows prolonged monitoring, bilateral monitoring, and allows bedside removal of the electrodes if no surgery is indicated.